(1) Field of the Invention
The present invention relates to a polyamide molding material and a hollow-molded body obtained therefrom. More particularly, the present invention relates to a molding material capable of producing a hollow-molded body having an excellent gas barrier property (resistance to permeation of gases), and excellent mechanical characteristics and heat resistance.
(2) Description of the Related Art
Because of its excellent mechanical and chemical properties, polyethylene terephthalate is widely used as fibers, films, and industrial resins. Recently, polyethylene terephthalate has also been used for the production of vessels such as bottles and cups. In this field of application, from the view point of preservation of the contents, a gas barrier property is required. Polyethylene terephthalate has a higher gas barrier property than polyolefin resins such as polyethylene, but the gas barrier property of polyethylene terephthalate is unsatisfactory when compared with the gas barrier property of glass, aluminum or the like.
Methods for improving the gas barrier property of polyethylene terephthalate have been examined and many proposals have been made. For example, there have been proposed a process in which a polyester is coated or laminated with a gas barrier material such as polyvinylidene chloride or a saponified ethylene/vinyl acetate copolymer (Japanese Unexamined Patent Publications No. 54-117868 and No. 56-64839); a process in which a polyester is blended with a gas barrier material (Japanese Unexamined Patent Publication No. 57-19640); and, a process in which the gas barrier property is improved by increasing the orientation degree of a polyester molded body (Japanese Unexamined Patent Publication No. 56-15148). However, in the process in which the orientation degree is increased, the improvement of the gas barrier property is limited, and in the process in which a gas barrier material is used, the adhesion and heat resistance are unsatisfactory, and accordingly, the development of a gas barrier material having enhanced characteristics is desired.